This invention relates to a rotary head assembly to be used to record and reproduce signals in magnetic tapes in digital audio tape recorders (DAT) and the like.
In digital audio tape recorders and the like, the band of signals to be recorded is so wide that it is necessary to elevate the relative speed between the magnetic tape and magnetic head and therefore a rotary head system rotating the magnetic head is generally adopted. Also, an oblique scanning in which the scanning line is made obligue is adopted to take the recording time of the magnetic tape to be long.
FIG. 22 shows the essential part of a conventional digital audio tape recorder adopting a rotary head system. In the drawing, a rotary head 30 is provided as inclined with respect to a tape cassette 32 containing a magnetic tape 31. The magnetic tape 31 pulled out of the tape cassette 32 is obliquely wound on a drum 30a of the rotary head 30 through an inlet tape guide roller 34 and inlet side inclined guide 35 provided on a body 33 of the digital audio tape recorder and is returned to the tape cassette 32 as held by a capstan shaft 38 and pinch roller 39 through an outlet side inclined guide 36 and outlet tape guide roller 37. By the way, the inlet inclined guide 35 and outlet inclined guide 36 are guides for obliquely winding on the drum 30a without loosening the magnetic tape 31 parallelly wound and contained in the tape cassette 32.
FIG. 23 shows the rotary head 30 formed of an upper drum 30A rotating at a high speed with a power obtained by a motor shaft 40 and moter part 41 and a lower drum 30B on the fixed side. A magnetic head 42 is provided as exposed on the periphery of the upper drum 30A. The lower drum 30B is proved with a leading groove 43 so that the magnetic tape 31 may be wound on the drum 30a at a predetermined angle of inclination. The magnetic tape 31 is positioned as held by flanges 34b and 37b provided respectively on the inlet tape guide roller 34 and outlet tape guide roller 37 and the leading groove 43 so as to run stably.
In the above described conventional formation shown in FIG. 22 and 23, the drum 30a of the rotary head 30 is of a two-step formation of the upper drum 30A and lower drum 30B and is inclined obliquely with respect to the tape case and therefore there has been a defect that the apparatus can not be made small in the size. Also, a plastic molding is considered to reduce the cost and weight of such rotary head 30 but, as the upper drum 30A and lower drum 30B are precisely worked and rotated, there is a defect that it is difficult to guarantee the precision of working them.
Also, in a helical scanning system developed with such video tape recorder as is described above as a center, as the angle of winding the magnetic tape 31 on the drum 30a of the rotary head assembly 30 is larger than about 180 degrees, such guide parts as the inlet tape guide roller 34, inlet inclined guide 35, outlet inclined guide 36, outlet tape guide roller 37 and pinch roller 39 must be moved along a predetermined track to pull out the magnetic tape 31 to the illustrated position from the initial tape position a within the tape cassette 37 and wind it and therefore there has been a defect that it is difficult to meet the positioning precision required therefor.
Further, plasticizing is expected from the object of making the rotary head assembly light. However, in the conventional structure, such many problems as of the precison, the phase detection of the motor rotating the rotating disc and the static electricity by the friction produced by the magnetic tape made of plastics are left unsolved.